#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Time    : 2020/7/3 20:09
# @USER    : Shengji He
# @File    : ConvertSortedArray2BinarySearchTree.py
# @Software: PyCharm
# @Version  : Python-
# @TASK:
from typing import List


# Definition for a binary tree node.
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None


class Solution:
    def sortedArrayToBST(self, nums: List[int]) -> TreeNode:
        """
        Given an array where elements are sorted in ascending order, convert it to a height balanced BST.

        For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the
        two subtrees of every node never differ by more than 1.

        Example:
            Given the sorted array: [-10,-3,0,5,9],

            One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST:

                  0
                 / \
               -3   9
               /   /
             -10  5

        :param nums:
        :return:
        """
        def helper(left, right):
            if left > right:
                return None
            mid = (left + right) // 2
            root = TreeNode(nums[mid])
            root.left = helper(left, mid - 1)
            root.right = helper(mid + 1, right)
            return root
        return helper(0, len(nums) - 1)



if __name__ == '__main__':
    print('done')
